Automated data storage libraries are known for providing cost effective storage and retrieval of large quantities of data. The data is stored on data storage media that is typically contained within a cartridge and referred to as a data storage media cartridge. The media comprises magnetic media (such as magnetic tape or disks), optical media (such as optical tape or disks), electronic media (such as PROM, EEPROM, flash PROM, Compactflash™, Smartmedia™, Memory Stick™, etc.), or other suitable media. The data storage library contains data storage drives that store data to, and/or retrieve data from the data storage media. The cartridges are stored inside the library in storage shelves when not in use by the data storage drives. One or more robot accessors retrieve selected cartridges from the storage shelves and provide them to data storage drives. Generally, data storage libraries contain a large number of storage shelves to place the cartridges when the cartridges are not in use by a data storage drive. Each storage shelf that may contain a cartridge is referenced or located by the library by a storage shelf address. The data storage library typically includes control electronics that direct the accessors operation, communicate with the data storage drives and interface to one or more host computers to transfer commands and/or data between the host computer and the data storage library. Typically, data stored on data storage media of an automated data storage library, once requested, is needed quickly. Thus, it is desirable that an automated data storage library be maintained in an operational condition as much as possible, such as the well known “24×7×365” availability.
Various companies manufacture automated data storage libraries, and each company has libraries with different features. Early data storage libraries could only operate with a single host computer. Automated data storage libraries now offer the capability of sharing the entire library with a plurality of host computers. Any host computer that is attached to the library may obtain access to all, or part of the cartridges in the library. The IBM 3584 UltraScalable Tape Library is an example of a product that has the internal capability to allocate data storage drives and storage shelves to multiple host computers. The data storage library can be divided into one or more logical libraries, where the robotics and electronics are usually shared throughout the library; however, the storage shelves and data storage drives are assigned to one of the logical libraries and are not shared.
The library system can include several frames each storing different media types. In a mixed media library installation, each frame supports only one media type. The installation order of the frames is not limited thereby presenting a difficulty when a logical library spans from one frame to a subsequent frame where an intervening frame supporting a different media type is being used. Storage shelf addresses are typically assigned in sequential order as storage shelves are encountered within each frame. For example, if each frame contains 100 storage shelves, and there are four frames in a library, the storage shelf address range of frame number one could be from one to 100. The storage shelf address range of frame two would then be from 101 to 200 and so on, with all of the four frames each handling 100 storage shelves up to frame four. The host computer cannot use the data storage library if there is a gap in the storage shelf range. This physical arrangement of storage shelves can further be broken down into multiple logical libraries wherein of the 400 storage shelves described above, logical library one may include the range of elemental addresses from 1 to 50. Logical library two handles the elemental address range from 51 to 300 and logical library three could handle elemental addresses from 301 to 400. The host computer operates the three logical libraries as three different libraries even though they are enclosed within one physical structure.
The present invention solves the problem where, for example, frames one and three are of one media type and frames two and four are of another media type. Storage shelf addresses in prior art systems are assigned in the sequential order of the frames and therefore a host in this example cannot use the storage shelves in frames one and three simultaneously as frame two consists of a different media type. For a host to contain more than the 100 storage shelves of this example available in frame one, a physical reconfiguration would be required to switch frames two and three thus providing up to 200 contiguous storage shelves of the same media type. Therefore, there is a need to configure a library system to operate with mixed media without requiring that the frames of the same media type be sequentially mounted.